[PATCH] mm: fix z3fold warnings on CONFIG_SMP=n

["Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>]

Spinlocks are always lockable on UP systems, even if they were just
locked.

Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
---
 mm/z3fold.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 4b366d181..4e6ad2de4 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -202,6 +202,13 @@ static inline void z3fold_page_lock(struct z3fold_header *zhdr)
 	spin_lock(&zhdr->page_lock);
 }
 
+static inline void z3fold_page_ensure_locked(struct z3fold_header *zhdr)
+{
+#ifdef CONFIG_SMP
+	WARN_ON(z3fold_page_trylock(zhdr));
+#endif
+}
+
 /* Try to lock a z3fold page */
 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
 {
@@ -277,7 +284,7 @@ static void release_z3fold_page_locked(struct kref *ref)
 {
 	struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 						refcount);
-	WARN_ON(z3fold_page_trylock(zhdr));
+	z3fold_page_ensure_locked(zhdr);
 	__release_z3fold_page(zhdr, true);
 }
 
@@ -289,7 +296,7 @@ static void release_z3fold_page_locked_list(struct kref *ref)
 	list_del_init(&zhdr->buddy);
 	spin_unlock(&zhdr->pool->lock);
 
-	WARN_ON(z3fold_page_trylock(zhdr));
+	z3fold_page_ensure_locked(zhdr);
 	__release_z3fold_page(zhdr, true);
 }
 
@@ -403,7 +410,7 @@ static void do_compact_page(struct z3fold_header *zhdr, bool locked)
 
 	page = virt_to_page(zhdr);
 	if (locked)
-		WARN_ON(z3fold_page_trylock(zhdr));
+		z3fold_page_ensure_locked(zhdr);
 	else
 		z3fold_page_lock(zhdr);
 	if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
-- 
2.19.0